1. Field of the Invention
The present invention generally relates to the field of mechanical apparatus' usable for rotating fluid controlling vanes, such as those used in turbine engines. More specifically, the present invention relates to a novel apparatus which utilizes piezoelectric, piezo stack, piezoceramic, magnetostrictive or other reduced size actuators to rotate one or more vanes, such as for example compressor stator vanes and/or inlet guide vanes in small turbine engines. The use of piezoelectric, piezo stack, piezoceramic, magnetostrictive or other reduced size actuators to rotate one or more actuated compressor stator vanes and/or inlet guide vanes in turbine engines allows reduced size and weight for such actuators which in turn enables smaller, lighter turbine engines that have numerous applications but are especially well adapted for use in small aircraft and Unmanned Air Vehicles (UAVs) or drones. In such applications, the fluid controlling vanes are typically inlet guide vanes or compressor stator vanes.
2. Background
Vanes for fluid control are used in numerous applications. It is often desirable in many applications that such vanes be controllable for purposes of rotating such vanes about an axis in order to achieve desired characteristics of the flow of the affected fluid. Such rotation may be used, for example, to reduce turbulence and increase desirable laminar flow of a fluid, which in turn may reduce drag and increase the effectiveness of the system that is making use of the fluid. The scope of the present invention is such that it is usable in any application where such fluid control is desired. One such application is the field of small jet turbine engines used for the propulsion of aircraft: in such application the fluid is air, and the desire is to effectuate certain desirable properties of the air that is entering the engine intake and progressing through the following compression and other jet turbine stages.
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work. Turbine engines for use as propulsion systems for aircraft are well known in the art. Such engines have been adapted for various sizes of manned aircraft and other vehicles and are typically comprised of an upstream compressor section coupled to a downstream turbine with a combustion chamber in-between.
The compressor section of a turbine engine increases the pressure and conditions airflow before the air enters the combustion chamber. The airflow entering the compressor is often turbulent due to the high angle of incidence between engine inlet and free-stream velocity, or existing atmospheric turbulence. Additional factors or operational changes that may influence or affect turbine engines include but are not limited to inlet air speed, air temperature, humidity, density, and the like. It is desirable to effectuate control over the inlet air dynamics in order to increase the efficiency of operation of the turbine engine: to this end, devices termed “inlet guide vanes”, or IGVs, are sometimes incorporated into the engine design. Inlet guide vanes are typically placed in the intake air flow in front of the compressor section of a turbine engine in order to better direct air flow into the compressor sector and to reduce the turbulence of the incoming air. Actuated, or variable, IGVs are IGVs that are typically rotatable on an axis that is radially oriented to the axis of the turbine engine. Variable IGVs are rotated (or, in other words, pivoted) about their axis in order to increase their effectiveness in reducing the turbulence of the intake air flow. The rotating of variable IGVs allows the angle of attack of IGVs to be optimized relative to the direction of flow of the intake air. The rotating feature of variable IGVs is thus used to help control the relative angle of incidence of the flow that enters the engine compressor, thereby preventing flow separation, compressor stall, and further extending the compressor's operating envelope.
For the same reasons, variable, or rotating, Compressor Stator Vanes (CSVs) are desirable to aid in optimizing the air flow and reducing turbulence in the compressor stage of a jet turbine engine.
Conventional large scale turbine jet engines that generally employ variable IGVs have been developed by Rolls Royce in their Trent DR-900 and General Electric in their model J79. The original engine employing variable IGVs was the General Electric model J73 turbojet engine. Current actuation of CSVs or IGVs on such large scale engines is routinely performed by servomotor or hydraulic means. Such servomotor or hydraulic actuation in large scale jet engines, however, cannot be functionally translated into smaller jet engine applications due to the severe size and weight constraints that are imposed upon these smaller engines. The hydraulic pump, fluid lines, and actuators are simply too large and heavy for small jet turbine applications. The same is true for servomotor actuation systems: the controllers, motors, wiring and actuators of servomotor actuation systems exhibit the same weight and size problems as hydraulic systems when considered for small jet turbine engines. There are other problems with these legacy actuation systems as well. Hydraulic actuation of small (e.g. 5-cm long) vanes is difficult to achieve due to geometric scaling. Geometric down scaling of hydraulic circuit components for small engines would imply very small-diameter hydraulic lines and naturally lead to fluid friction losses. Additionally, as stated above servomotors are generally too heavy (due to coils, magnets, and the like) to be useful in small jet engine applications. Jet engines designed especially for UAVs are characterized by thrust force on the order of 100N and, due to their size and weight limitations, lack advanced flow control devices such as inlet guide vanes and/or compressor stator vanes. There is therefore a need for an improved, light weight system and apparatus for implementing variable IGV were available, smaller aircraft would reap the benefits of the performance improvements afforded by variable IGV and/or CSV.
An example of a vehicle that would benefit from the downsizing and reduction in weight and size of variable IGV and CSV assemblies is the Unmanned Aerial Vehicle (UAV), or drone. UAVs have gained popularity in recent years to become an indispensable part of aerial missions that may include reconnaissance, surveillance, law enforcement, border patrol, communication support, and the like. As a result, advancements in small jet-engine performance, and reduction in size and weight, are needed to increase the performance (range, payload and efficiency) of the UAV.
Variable inlet guide vane actuation systems and control methods of the prior art have been described but are not well adapted to small lightweight applications. For instance, U.S. Pat. No. 3,628,329 to Spencer describes an inlet guide vane actuator comprised of a which positions an element upon sensing a parameter and, after a certain time limit has elapsed, automatically repositions the element to its initial position. A central solid rod is surrounded by a thin perforated sleeve constructed of material having the same coefficient of expansion as the rod. The rod and sleeve are rigidly interconnected at one end, and hot gas is passed in a swirling manner along the axis of the actuator. The time differential expansion of the two members is utilized to initially position and then reposition a controlled element. However the apparatus of this invention does not allow for instantaneous and controlled positioning of an IGV or CSV, and furthermore may be of such size as to be unusable in small turbine engines.
A system for controlling the motion of turbomachinery is disclosed in U.S. Pat. No. 5,141,391. This U.S. patent discloses a control system that actively controls at least one troublesome mode of an unsteady motion phenomenon in turbomachinery in order to enable an increase in the operating range of the turbomachinery. For example, rotor blade flutter or rotating stall may be controlled in a turbocompressor. The control system has a control bandwidth which is at least partly coextensive with the bandwidth of the unsteady motion phenomenon and operates by passing sensor signals related to the unsteady motion phenomenon from a sensor array in the turbomachine to a mode filter which produces a signal or signals which are related to the troublesome mode or modes. The selected mode signals are amplified and phase-shifted by time-variable amounts so as to produce control signals having controlled amplitude and phase relationship to the troublesome mode. Actuators in an actuator array may be continuously driven by the control signals and produce physical effects in the turbomachine which act counter to the troublesome mode without exciting others. While this U.S. patent discloses a method for controlling actuation of components of a turbomachine such as a turbine engine, it does not disclose mechanisms for achieving the rotation of inlet guide vanes or compressor stator vanes and thus does not answer the need for reduced size and weight vane actuation systems.
U.S. Pat. No. 7,096,657 to Mahoney et al. discloses an inlet guide vane actuation system that achieves positioning of inlet guide vanes in a gas turbine engine into open, intermediate and closed positions. This U.S. patent discloses an electromechanical inlet guide vane actuation system that includes one or more electric motor driven actuators that are used to appropriately position the inlet guide vanes in a gas turbine engine. The actuation system includes a control circuit that supplies guide vane actuation control signals in response to guide vane position command signals it receives. The guide vane actuation control signals are supplied to one or more electric motors, which position actuators, and thus the inlet guide vanes, to the commanded position. The electromechanical components of this system are adapted to large gas turbine engines and do not achieve the size and weight reductions necessary to be compatible with very small turbine engines.
U.S. Pre Grant Publication No. US2009/0297334 describes a sensing and control method for determining a desired positioning for inlet guide vanes. However, this disclosure does not disclose an apparatus for positioning guide vanes to a desired position.
A need therefore exists for a technology innovation and improvement upon the state of the prior art that would allow variable IGVs and/or CSVs on smaller jet engines (for example, but not by way of limitation, 20-200 lb thrust), such as in increasingly popular UAV applications, where servomotor/hydraulic actuation is either impossible or very difficult to implement on the smaller engines due to size issues, weight tolerances, frictional losses, and the like.